In the manufacture of integrated circuits (ICs) and other electronic devices, testing with automatic test equipment (ATE) is performed at one or more stages of the overall process. A special handling apparatus is used to place the device under test (“DUT”) into position for testing. In some cases, the special handling apparatus may also bring the DUT to the proper temperature and/or maintain it at the proper temperature to be tested. The special handling apparatus is of various types including “probers” for testing unpackaged devices on a wafer and “device handlers” for testing packaged parts; herein, “peripheral” or “peripherals” will be used to refer to all types of such apparatus. The electronic testing itself is provided by a large and expensive ATE system. The DUT requires precision, high-speed signals for effective testing; accordingly, the “test electronics” within the ATE, which are used to test the DUT, are typically located in the test head, which must be positioned as close as possible to the DUT. The test head is extremely heavy; the size and weight of the test heads have grown from a few hundred pounds to as much as three to four thousand pounds.
In order to use a test head to test integrated circuits, the test head is typically “docked” to a peripheral. When docked, the test head must be located as close as possible to the peripheral's test site in order to minimize signal degradation. A test head positioning system may be used to position the test head with respect to the peripheral and may be designed to facilitate flexible docking and undocking of a test head with a variety of peripherals. A test head positioning system may also be referred to as a test head positioner or test head manipulator. Test head positioning systems have been described in numerous patents, and certain patents of interest will be mentioned later.
Docking is well known and documented in the patent literature. For example, U.S. Pat. No. 4,589,815 (Smith) describes an early docking system whose principles are still in general use. Additionally, WIPO International Publications WO 03/008984 A2 (Gudin et al), WO 02/25292 A2 (Ny et al) and WO 01/64389 A2 (Holt et al), provide more general discussions of contemporary docking and include several further references. Some pertinent concepts are summarized where appropriate in the following discussions.
It is often desirable to dock a given test head with different peripherals from time to time. For example, testing may be performed with a certain packaged device handler for a time, and then it may be desired to change to another packaged device handler. In other situations, it may be desired to change between a wafer prober and a packaged device handler. In such cases the test head is undocked from the original peripheral which is then moved out of the way. The new peripheral is then moved into place, and the test head is docked with it. Also, it is often desirable to move the test head away from a peripheral to perform maintenance. Thus, it may be required to easily dock and undock the test head with a variety of different peripherals.
An electrical interface apparatus is also provided to enable electrical signals, grounds, and power to be passed between the test electronics and the DUT. Typically a portion of the interface is coupled to the peripheral and the remaining portion is coupled to the test head. Electrical contacts are disposed on each side of the interface. The interface may include hundreds or thousands of electrical contacts, which are of necessity small and fragile. Typically, the contacts are arranged in a generally planar fashion on each side of the interface. When the test head is docked, electrical connections are thus made between corresponding contacts on the two sides of the interface. It is well understood that in docking the test head must first be planarized with respect to the interface, aligned linearly in two dimensions, and aligned rotationally about an axis perpendicular to the plane of the interface. The test head may then be advanced along a linear path into a docked position. The docking apparatus must provide a means to establish the final docked distance (or “height”) between the test head and the peripheral such that the electrical contacts are satisfactorily mated (that is, with sufficient compression, scrub, etc. to assure a low resistance connection) and such that the test head does not over-travel and thus damage or destroy the contacts. It is typical that interfaces will be changed when operation is switched from one peripheral to another. Further, it is typical that when a single peripheral is used to first test devices of one type and then reconfigured to test devices of another type, the interface is changed from a first type to a second type. Generally, the docked height requirement may be different for each testing set up.
The test head positioning system is a mechanical device that allows an operator to bring an automatic test equipment test head, which may weigh close to three to four thousand pounds, into proximity with a peripheral and to allow the test head to be docked with it. When the test head is docked with the peripheral, the hundreds or thousands of delicate electrical contacts must be precisely aligned and mated to enable testing signals, grounds and power to be transferred between the DUT and the test head. The size, weight, number and resiliency of the cables that connect the test head to the automatic test equipment have correspondingly increased. The resultant effect of these factors have made it increasingly difficult to bring a heavy test head into contact with a peripheral with the precision needed to mate hundreds or thousands of individual delicate electrical contacts without damaging them.
Furthermore, although there have been limited attempts to provide multiple-height docking apparatus that allows the docked height to be adjusted or selected, it is presently customary to use single-height docking apparatus having a single, built in docking height. This is because the mechanisms employed in multiple-height docks have proven to be limited in operation or difficult to effectively operate. Typically single-height docks are specifically designed for each user application. Thus, when changing over from one testing set up to another it has become necessary to change docking apparatus. Also the cost and storage requirements for a large number of docking apparatuses can become appreciable.
These factors have created demand for test head positioning systems with an increased load carrying capacity, increased flexibility in carrying different peripheral devices and increased protection from damaging the fragile electrical connections.